Gluster users - Apr 2014 - How should ps's VSZ and RSS be interpreted for Gluster?

Hi,

I've got a smallish Gluster 3.1.5 instance across two systems with most of
the
service being by NFS mounts. Yeah, that's old. But it's generally stable
and
there are other priorities ahead of upgrading it. 

Recently it started to lag on directory listings on the box providing
Gluster's NFS mounts. The current %CPU and %MEM readings in ps looked
modest, but the VSZ and RSS (aka VIRT and REZ in htop) readings were way
into what looked like impossibly high figures. Restarting Gluster brought
those down, and I hope will turn out to fix the sluggish directory listings
(seems to, but they were intermittent).

Trying to understand this better, I've found this article:

  http://emilics.com/blog/article/mconsumption.html

So I have a rough idea, but I'm still not entirely clear on what it means
when over many months those VSZ and RSS values go way up for a process, and
what defines sanity for those processes for Gluster, as compared to the
danger zone where I really had better restart the thing.

If someone can suggest a rule-of-thumb way to calculate the threshold of
insanity for these, I'll probably write up a simple Nagios plugin to watch
for that being approached, to remind me to restart Gluster before the users
start complaining again. 

Thanks,
Whit